1. Field of the Invention
The invention relates to a process for application of a free-flowing material on the inner surface of a tube blank and to a device for performing the process.
2. Background Art
A process is known for descaling the inner surface of red-hot hollow billets in the production of seamless tubes. In such process for application of a free-flowing material to the inner surface of a tube blank with a continuous, at least approximately cylindrical hollow space, a carrier gas stream laden with the material is conducted axially through the hollow space after imparting of a swirl. The device for performance of the process has a passage element for the carrier gas stream laden with the material, in whose passage space a swirl-producing device is placed. See European Published Application No. 0133937.
In such process and with such device, the carrier gas stream laden with the material, namely, a descaling agent, is conducted with the swirl directly through the tube blank, namely, the red-hot hollow billet. Thus, by means of the swirl, a more uniform distribution of the material in the carrier gas is achieved and, by the centrifugal force resulting from the swirl, a considerable part of the material is brought to the inner surface of the tube blank, without obeying the forces of gravity.
The laden carrier gas stream with the swirl must first drive the stagnant air in the hollow space through and from the hollow space. Thus, a part of its swirl is transferred to the stagnant air and is lost for the applying of the material to the inner surface of the tube blank. When the laden carrier gas stream flows through the hollow space its speed and its swirl are smaller near the inner surface than in the center of the hollow space cross section. The flow becomes laminar because of the friction on the inner surface, especially if the surface, e.g., in he case of a hollow billet, is coarsely covered with a layer of scale. Altogether only a part of the swirl imparted to the laden carrier gas stream is effective in applying the material to the inner surface.